sleep.js: Example of a sleep function in js (for async functions) IIFE: Sometimes you see online the term IIFE. This example shows what it is. - Immediately invoked function expression. Execute a function directly. Optional chaining: - // The optional chaining operator (?.) permits reading the value of a property located deep within a chain of connected objects without having to expressly validate that each reference in the chain is valid. - object.property?.property logical OR (||) - expr1 || expr2 const vs let: When searching online, you see a lot of wrong usage of let and const variables (mostly with objects). A lot of people do let myObject = {}. As long as they do not replace the whole object, const is better. The file also contains other examples. promises: A small example of how to write promises. promises orders folder: Contains 3 cases of how the execution order is of the promises. You can test them by yourself by using "node case1.js" for example. - case 1: Example of promises that wait for each other - case 2: Execute all promises at once - case 3: Use promise.all to wait for all promises to resolve, before continuing. await: Example of async / await with the promises as example.